Group III nitrides such as Gallium Nitride (GaN) and related III-V alloys are highly desirable materials for semiconductor devices and particularly for high temperature and high frequency applications. In many semiconductor devices such as, for example, lateral Field Effect Transistors (FETs) for high frequency applications, a semi-insulating GaN buffer layer is highly desirable. Due to the lack of large area native GaN substrates, semi-insulating GaN is most often grown on a heteroepitaxial substrate such as Silicon Carbide (SiC) or sapphire. The use of a heteroepitaxial substrate is problematic due to lattice mismatch between the heteroepitaxial substrate and the GaN. As such, the GaN must be grown to a sufficient thickness to overcome the tension or stress induced by the lattice mismatch. Further, because epitaxially grown GaN includes impurities, the GaN must be sufficiently doped to become semi-insulating. For example, U.S. Pat. No. 7,170,095 entitled “Semi-Insulating GaN and Method of Making the Same,” which issued Jan. 30, 2007 and is hereby incorporated herein by reference in its entirety, describes methods of making semi-insulating GaN using a deep acceptor dopant such as, for example, Manganese (Mn), Iron (Fe), Cobalt (Co), Nickel (Ni), Copper (Cu), or the like to compensate for donor impurities in the GaN. Each dopant typically has advantages and disadvantages. As such, there is a need for improved doping for a semi-insulating Group III nitride and, in particular, improved doping for semi-insulating GaN.